Image enhancement, expressed in improved image quality, is an ever-lasting quest in the construction of optical systems. Image quality may be represented by one or more characterizing parameters such as depth-of-focus, distortion, aberrations-related-blur, SNR or resolution, and the image improvement may be the result of an improvement in one or more of such parameters. Thus, for example, various optical components may be incorporated in an optical system with the aim of reducing aberrations. Various types of lens coating or other optical correctors (e.g. lenses) may be used with an imaging lens unit to reduce chromatic and/or spherical aberrations (coma or other blur sources) caused by the imaging lens unit.
In recent years, image processing techniques are also becoming a common tool used to enhance images, and significant improvement of images obtained from a given optical system may indeed be achieved by performing appropriate image post-processing on such images. The miniaturization of computerized processors and the subsequent proliferation of such processors in commercial commodities such as digital and video cameras, cellular phone cameras etc., have expedited the incorporation of computerized image enhancement utilities in such devices.
It is known to use an aperture coding (e.g. phase-coding) within the optical system and/or appropriate image processing, to improve the image quality. For example, U.S. Pat. No. 6,842,297 discloses Wavefront Coding Optics, which applies a phase profile to the wavefront of light from an object to be imaged, retain their insensitivity to focus related aberrations, while increasing the height of the resulting Modulation Transfer Functions (MTFs) and reducing the noise in the final image. US 2008/0131018 describes an image reconstruction technique utilizing algorithm applied on phase encoded image data to obtain an image in which the effects of phase perturbation are removed. This technique includes estimation of a degree of defocus in the obtained image, adjustment of the reconstruction algorithm to take into account the estimated degree of defocus, and application of the adjusted reconstruction algorithm to obtain a restored image.